Copper residue chamber clean

ABSTRACT

Methods of removing copper residue from interior surfaces of an etch process chamber are described. A plasma treatment using halogen-containing precursors transforms the copper residue into halogen-copper complexes. Plasma-excited inert gases are used to desorb the halogen-copper complexes. In this way, the copper residue is removed from the interior surfaces of the etch process chamber.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Prov. Pat. App. No. 61/825,834 filed May 21, 2013, and titled “COPPER RESIDUE CHAMBER CLEAN” by Hoinkis et al., which is hereby incorporated herein in its entirety by reference for all purposes.

FIELD

The present invention relates to substrate processing.

BACKGROUND

The use of copper as a conductive interconnect material is favored in semiconductor devices because of the high conductivities and circuit speeds copper enables. On the other hand, copper is difficult to pattern and copper interconnect leads have predominantly heretofore been formed using damascene and dual damascene processing technology whereby openings are formed in a dielectric layer on a substrate such as a semiconductor substrate used to form semiconductor devices. Copper is deposited over the dielectric layer and within the openings. Polishing/planarization removes copper from over the dielectric leaving the copper inlaid within the openings. In this way, the burden on photolithography is shifted from copper to the more manageable dielectric layer. The inlaid copper includes an upper surface that is essentially co-planar with the top surface of the patterned dielectric layer in which the copper is formed.

Subtractive copper etching is the alternative to a damascene process flow. A layer of copper is deposited and then patterned to form horizontal electrical interconnections. Early attempts to investigate subtractive copper etching used plasma excited halides which were found to provide many advantages but degraded the physical integrity of the copper near grain boundaries and other seams. There is renewed interest in subtractive copper etching since progress has been made in addressing these shortcomings. This renewed interest in subtractive copper etching brings renewed interest in associated properties of such a process. Thus, there is a need in the art to develop maintenance procedures unique to subtractive copper etching.

SUMMARY

Methods of removing copper residue from interior surfaces of an etch process chamber are described. A plasma treatment using halogen-containing precursors transforms the copper residue into halogen-copper complexes. Plasma-excited inert gases are used to desorb the halogen-copper complexes. In this way, the copper residue is removed from the interior surfaces of the etch process chamber.

Embodiments of the invention include methods of cleaning a dielectric window of a substrate processing chamber having a substrate processing region. The method includes flowing a halogen-containing precursor into the substrate processing region while forming a first local plasma in the substrate processing region having a first local plasma power to form excited halogen-containing species. The method further includes flowing an inert gas into the substrate processing region while forming a second local plasma in the substrate processing region having a second local plasma power. The copper residue on interior surfaces of the dielectric window is transformed into a copper halogen layer during the first local plasma. The copper halogen layer is desorbed as desorbed species from the dielectric window during the second local plasma which occurs after the first local plasma.

Embodiments of the invention include methods of cleaning a dielectric window of a substrate processing chamber. The methods include flowing a halogen-free precursor into the substrate processing region while forming a subtractive etch local plasma in the substrate processing region having a subtractive etch local plasma power to form excited halogen-free species. The subtractive etch removes copper from a substrate and leaves a copper residue on the interior surfaces of the dielectric window. The substrate processing region is devoid of halogens during the subtractive etch local plasma. The methods further include removing the substrate from the substrate processing region. The methods further include flowing a halogen-containing precursor into the substrate processing region while forming a halogen local plasma in a substrate processing region having a halogen local plasma power to form excited halogen-containing species. The halogen local plasma transforms the copper residue on interior surfaces of the dielectric window into a copper halogen layer. The methods further include flowing an inert gas into the substrate processing region while forming an inert gas local plasma in the substrate processing region having an inert gas local plasma power. The copper halogen layer is desorbed as desorbed species from the dielectric window. The inert gas local plasma occurs after the halogen local plasma.

Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the embodiments. The features and advantages of the embodiments may be realized and attained by means of the instrumentalities, combinations, and methods described in the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the embodiments may be realized by reference to the remaining portions of the specification and the drawings.

FIG. 1 is a flow chart of a residual copper removal process according to embodiments.

FIG. 2 is a schematic of a etch process chamber which can be cleaned according to a residual copper removal process according to embodiments.

FIG. 3 is a schematic diagram of an etch process chamber which can be used to carry out processes according to embodiments.

FIG. 4 is a schematic top-view diagram of an exemplary multi-chamber substrate processing system which can be used to carry out processes according to embodiments.

In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

DETAILED DESCRIPTION

Methods of removing copper residue from interior surfaces of an etch process chamber are described. A plasma treatment using halogen-containing precursors transforms the copper residue into halogen-copper complexes. Plasma-excited inert gases are used to desorb the halogen-copper complexes. In this way, the copper residue is removed from the interior surfaces of the etch process chamber.

The processes disclosed herein remove remnants from interior surfaces of an etch process chamber. The interior surface is on a dielectric window which can be used to pass electromagnetic energy from inductive coils positioned outside the etch process chamber. Accumulation of copper residue has been found to absorb electromagnetic energy and may even cause heat buildup on the dielectric window during plasma excitation. Previously, methods of etching copper avoided forming copper residue by including halogen-containing precursors during the subtractive copper etch process and also by subtractive copper etching at high substrate/chamber temperatures. Inclusion of halogen-containing precursors and maintaining high substrate/chamber temperatures increased the volatility of etch by-products and increased the probability that etch by-products would be evacuated through a vacuum pump. Recent subtractive etch process development activity involves using halogen-free precursors and/or lower substrate/chamber temperatures. As a result, remnants of the copper etch (referred to herein as “copper residue”) may now be a problem which needs to be addressed. Copper residue accumulates on interior surfaces of the dielectric window during these more recent subtractive copper etch processes. Removing the copper residue, as taught herein, involves treating the interior surface of the etch process chamber to remove the copper residue after the previous substrate is removed and before a subsequent substrate arrives into the etch process chamber. Removing the copper residue enables plasma power to be efficiently transferred into the etch process chamber, facilitating processing of the subsequent substrate.

In order to better understand and appreciate the invention, reference is now made to FIG. 1 which is a flow chart of an exemplary residual copper removal process 100 according to embodiments. Reference will concurrently be made to FIG. 2 which shows a schematic of an exemplary etch process chamber 200 which may be used to perform exemplary copper residue removal processes. A wide variety of substrate processing chambers may also benefit from exemplary residual copper removal process 100. The first two operations are optional and represent one method of producing the undesirable copper residue on an interior surface of the etch process chamber 200. The exemplary substrate 206 is coated with a layer of copper and a patterned mask positioned atop the copper layer. The copper layer is etched (operation 110) to transfer the pattern of the mask into the copper and etch effluents are pumped out of substrate processing region 210 through vacuum pump 202. This pattern transfer etch may be referred to herein as a subtractive copper etch process.

During the subtractive copper etch process, the etch precursors are delivered through precursor/gas inlets 250 into substrate processing region 210. The etch precursors are excited by an inductively coupled plasma created by applying alternating current (AC) power 241 to inductive coils 240. The plasma may be referred to herein as a subtractive etch local plasma and is applied with a subtractive etch local plasma power. Electromagnetic radiation passes through dielectric window 220 which may also be referred to as a lid or a dielectric lid herein. Dielectric window 220 mates with metal chamber portion 201 to form the bulk of the etch process chamber 200. The etch precursor may be halogen-free and may include one or more of methanol (CH₃OH), ethane (C₂H₄), oxygen (O₂), hydrogen (H₂), carbon monoxide (CO), helium (He) or argon (Ar). Subtractive plasma excited halogen-free species etch copper from substrate 206 and leave a copper residue on the interior surfaces of the etch process chamber 200. Substrate processing region 210 may be devoid of halogens during operation 110 in embodiments. During this etch, residual copper accumulates on dielectric window 220 and metal chamber portion 201. The etched substrate 206 is removed from substrate pedestal 205 in operation 120.

Once substrate 206 is removed from substrate processing region 210, a plasma-excited halogen may be used to process the residual copper without damage to the seams and grain boundaries of the patterned copper layer. The substrate has been removed which makes it safe to introduce a halogen at this stage. Chlorine gas (Cl₂) is flowed into substrate processing region 210 through precursor/gas inlets 250 and excited in a first local plasma using inductive coils 240 (operation 130) in embodiments. Alternatively (or in combination) the chlorine gas may be excited in a first local capacitively-coupled plasma within substrate processing region 210 if the etch process chamber 200 is configured with the appropriate hardware. The substrate processing region 210 may contain other elements, for example, the substrate processing region 210 may contain chlorine and argon or may consist essentially of chlorine and argon in embodiments. The inclusion of the term “essentially” allows for unavoidable elemental concentrations and low concentrations which do not adversely affect the formation of a copper-halogen layer. The treatment using chlorine occurs during the first local plasma and subsequent processing occurs in operation 140 described below. The treatment operation 130 transforms adsorbed copper into adsorbed copper chloride on the surface of the dielectric window 220 and possibly the metal chamber portion 201 and other components as well.

In general, a halogen-containing precursor may be flowed (operation 130) into substrate processing region and the halogen-containing precursor comprises a halogen or may comprise at least one element from chlorine, bromine, and iodine. In embodiments, the substrate processing region may consist essentially of chlorine and an inert gas, halogen and an inert gas or chlorine and argon. Other components may reduce the ability of the halogen to form copper-halogen complexes in a copper halogen layer on the interior surfaces of the etch process chamber 200. The inclusion of the term “essentially” allows for other elemental concentrations which may be unavoidably present in a typical processing system as well as low concentrations which do not adversely affect the formation of the copper-halogen layer.

A flow of helium is then introduced into substrate processing region 210 (operation 140) where the helium is excited in a second local plasma struck within the substrate processing region 210. The second plasma may be created by the same excitation source and in the same rough location as the first plasma had been. In general the helium may be one or more inert gases, where inert gases include any gases which do not ultimately form covalent bonds within the copper or copper chloride on the interior surfaces of substrate processing region 210. The substrate processing region may consist essentially of inert gases, associated ions and desorbed species during operation 140 in some embodiments. The inert gas may include one or more of neon, helium, argon, xenon and the like. The second local plasma may consist essentially of inert gases. The substrate processing region may comprise helium and may consist essentially of helium during operation 140 in embodiments. In embodiments, the inert gas or the substrate processing region consists essentially of argon, consists essentially of neon or consists essentially of xenon. The inert gas or substrate processing region consists essentially of helium, argon, neon and/or xenon in embodiments of the invention.

Operation 140 is effective if a flow of one or more of hydrogen (H₂), HCl, HBr, and HI are also flowed into the substrate processing region in addition to the inert gases already mentioned. As such, the substrate processing region consists essentially of hydrogen (H), halogens, inert elements and desorbed species during operation 140 in embodiments. Other components may reduce the ability of the inert gas (and possibly HCl, HBr or HI) to desorb the copper-halogen complexes in a copper halogen layer on the interior surfaces of the etch process chamber 200. The inclusion of the term “essentially” allows for other elemental concentrations which may be unavoidably present in a typical processing system as well as low concentrations which do not adversely affect the desorption of the copper-halogen layer.

Operation 140 selectively removes copper chloride from substrate processing region 219 and may do so without removing copper or other metals from the chamber walls in embodiments. Generally speaking, operation 140 desorbs copper-halogen material from the chamber walls. The substrate processing region may be devoid of halogens during operation 140 aside from the desorbed species in embodiments. Desorbed species of the copper halogen layer are exhausted from the substrate processing region during or after operation 140 in embodiments.

The method includes applying energy to the halogen-containing precursor in the first local plasma and to the inert gas (e.g. helium) in the second local plasma while in the substrate processing region to generate the radicals used to treat and etch the interior surfaces of the substrate processing chamber. The plasma may be generated using known techniques (e.g., radio frequency excitations, capacitively-coupled power, inductively coupled power, and the like). In an embodiment, the energy is applied using an inductively-coupled plasma power supply unit 241. The AC power is supplied to the inductive coils 240 shown in cross-section in FIG. 2. The first local plasma power may have a first local plasma power which is less than a second local plasma power of the second local plasma. The first local plasma power may be between about 50 watts and about 2500 watts, between about 100 watts and about 2000 watts, between about 150 watts and about 1500 watts, or between about 250 watts and about 1000 watts in embodiments of the invention. The second local plasma power may be between about 100 watts and about 5000 watts, between about 200 watts and about 4000 watts, between about 300 watts and about 3000 watts, or between about 500 watts and about 2000 watts in embodiments of the invention. In embodiments, no DC accelerating voltage may be applied between substrate pedestal 205 and metal chamber portion 201 in order to ensure effective reaction of first local plasma and second local plasma with interior chamber walls. The pressure in the substrate processing region may be between about 0.5 mTorr and about 500 mTorr, between about 2 mTorr and about 200 mTorr or between about 5 mTorr and about 100 mTorr in embodiments, during either the operation 130 or operation 140.

The RF frequency applied for either the local or remote plasmas described herein may be low RF frequencies less than about 200 kHz, high RF frequencies between about 10 MHz and about 15 MHz, or microwave frequencies greater than or about 1 GHz in embodiments.

The flow of the halogen-containing precursor may further include one or more relatively inert gases such as He, N₂, Ar. The inert gas can be used to improve plasma stability, process uniformity and the like. Argon is helpful, as an additive, to promote the formation of a stable plasma. Process uniformity is generally increased when helium is included. These additives are present in embodiments throughout this specification. Flow rates and ratios of the different gases may be used to control etch rates and etch selectivity.

In embodiments, the halogen-containing precursor (e.g. Cl₂) is supplied at a flow rate of between about 5 sccm (standard cubic centimeters per minute) and 400 sccm, and argon at a flow rate of between about 0 slm and 1 slm. One of ordinary skill in the art would recognize that other gases and/or flows may be used depending on a number of factors including processing chamber configuration, substrate size, geometry and layout of features being etched, and the like. With regard to operation 140, the inert gas (e.g. helium) is supplied at a flow rate of between about 50 sccm (standard cubic centimeters per minute) and 2 slm in embodiments of the invention. The temperature of the substrate may be between about −20° C. and about 200° C. during both the halogen treatment operation (operation 130) and the residual copper removal operation (operation 140).

Additional considerations will be presented in the course of presenting an alternative exemplary substrate processing chamber as well as an exemplary substrate processing system which may be used to perform residual copper removal process 100.

Exemplary Processing Equipment

FIG. 3 depicts a schematic diagram of an etch process chamber 1001 which can be incorporated into a substrate processing system 1101 described later with reference to FIG. 4. Exemplary etch process chamber 1001 may also be referred to as a decoupled-plasma source chamber or DPS chamber. Etch process chamber 1001 includes inductive coils 1012, positioned exterior to a dielectric, dome-shaped ceiling 1020 (referred to herein as the dome 1020). Other chambers may have other types of ceilings, e.g., a flat ceiling. Inductive coil 1012 can be coupled to a radio-frequency (RF) source 1018 (that is generally capable of producing an RF signal having a tunable frequency). RF source 1018 is coupled to inductive coil 1012 through a matching network 1019. Etch process chamber 1001 can include a substrate support pedestal (cathode) 1016 that is coupled to a second RF source 1022 that is generally capable of producing an RF signal. RF source 1022 can be coupled to pedestal 1016 through a matching network 1024. Etch process chamber 1001 may also contain a conductive chamber wall 1030 that is connected to an electrical ground 1034. A controller 1040 including a central processing unit (CPU) 1044, a memory 1042, and support circuits 1046 for a CPU 1044 is coupled to various components of etch process chamber 1001 to facilitate control of the etch process.

In operation, a semiconductor substrate 1014 is placed on pedestal 1016 and gaseous components are supplied from a gas handling system 1038 to etch process chamber 1001 through entry port(s) 1026 to form a gaseous mixture 1050. Gaseous mixture 1050 is ignited into a plasma 1052 in etch process chamber 1001 by applying RF power from RF sources 1018 and 1022 respectively to inductive coil 1012 and pedestal 1016. The pressure within the interior of etch process chamber 1001 is controlled using a throttle valve 1027 situated between etch process chamber 1001 and a vacuum pump 1036. The temperature at the surface of chamber wall 1030 is controlled using liquid-containing conduits (not shown) that are located in chamber wall 1030 of etch process chamber 1001.

The temperature of substrate 1014 is controlled by stabilizing the temperature of pedestal 1016 and flowing helium gas from a helium source 1048 to channels formed by the back of substrate 1014 and grooves (not shown) on the pedestal surface. The helium gas is used to facilitate heat transfer between pedestal 1016 and substrate 1014. During the etch process, substrate 1014 is heated by a resistive heater within the pedestal to a steady state temperature and the helium facilitates uniform heating of substrate 1014. Using thermal control of both dome 1020 and pedestal 1016, substrate 1014 is maintained at a temperature of between about 100° C. and about 500° C.

FIG. 4 is a schematic top-view diagram of an illustrative multi-chamber processing system 1101. The processing system 1101 can include one or more load lock chambers 1102, 1104 for transferring of substrates into and out of the processing system 1101. Typically, since the processing system 1101 is under vacuum, the load lock chambers 1102, 1104 may “pump down” the substrates introduced into the processing system 1101. A first robot 1110 may transfer the substrates between the load lock chambers 1102, 1104, and a first set of one or more substrate processing chambers 1112, 1114, 1116, 1118 (four are shown). Each processing chamber 1112, 1114, 1116, 1118, can be outfitted to perform a number of substrate processing operations including the dry etch processes described herein in addition to cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, pre-clean, degas, orientation and other substrate processes.

The first robot 1110 can also transfer substrates to/from one or more transfer chambers 1122, 1124. The transfer chambers 1122, 1124 can be used to maintain ultrahigh vacuum conditions while allowing substrates to be transferred within the processing system 1101. A second robot 1130 can transfer the substrates between the transfer chambers 1122, 1124 and a second set of one or more processing chambers 1132, 1134, 1136, 1138. Similar to processing chambers 1112, 1114, 1116, 1118, the processing chambers 1132, 1134, 1136, 1138 can be outfitted to perform a variety of substrate processing operations including the dry etch processes described herein in addition to cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, pre-clean, degas, and orientation, for example. Any of the substrate processing chambers 1112, 1114, 1116, 1118, 1132, 1134, 1136, 1138 may be removed from the processing system 1101 if not necessary for a particular process to be performed by the processing system 1101. A copper etch processing chamber for carrying out the methods described and claimed herein may be installed in any one or more of substrate processing chamber locations.

System controller 1157 is used to control motors, valves, flow controllers, power supplies and other functions required to carry out process recipes described herein. System controller 1157 may rely on feedback from optical sensors to determine and adjust the position of movable mechanical assemblies. Mechanical assemblies may include the robot, throttle valves and susceptors which are moved by motors under the control of system controller 1157. A gas handling system 1155 is used to deliver halogen-containing precursors and inert species at various stages during the methods described herein.

In an exemplary embodiment, system controller 1157 includes a hard disk drive (memory), USB ports, a floppy disk drive and a processor. System controller 1157 includes analog and digital input/output boards, interface boards and stepper motor controller boards. Various parts of multi-chamber processing system 1101 which contains processing chamber 400 are controlled by system controller 1157. The system controller executes system control software in the form of a computer program stored on computer-readable medium such as a hard disk, a floppy disk or a flash memory thumb drive. Other types of memory can also be used. The computer program includes sets of instructions that dictate the timing, mixture of gases, chamber pressure, chamber temperature, RF power levels, susceptor position, and other parameters of a particular process.

A process for etching, depositing or otherwise processing a film on a substrate or a process for cleaning chamber can be implemented using a computer program product that is executed by the controller. The computer program code can be written in any conventional computer readable programming language: for example, 68000 assembly language, C, C++, Pascal, Fortran or others. Suitable program code is entered into a single file, or multiple files, using a conventional text editor, and stored or embodied in a computer usable medium, such as a memory system of the computer. If the entered code text is in a high level language, the code is compiled, and the resultant compiler code is then linked with an object code of precompiled Microsoft Windows® library routines. To execute the linked, compiled object code the system user invokes the object code, causing the computer system to load the code in memory. The CPU then reads and executes the code to perform the tasks identified in the program.

The interface between a user and the controller may be via a touch-sensitive monitor and may also include a mouse and keyboard. In one embodiment two monitors are used, one mounted in the clean room wall for the operators and the other behind the wall for the service technicians. The two monitors may simultaneously display the same information, in which case only one is configured to accept input at a time. To select a particular screen or function, the operator touches a designated area on the display screen with a finger or the mouse. The touched area changes its highlighted color, or a new menu or screen is displayed, confirming the operator's selection.

Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the disclosed embodiments. Additionally, a number of well known processes and elements have not been described to avoid unnecessarily obscuring the present invention. Accordingly, the above description should not be taken as limiting the scope of the invention.

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither or both limits are included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a process” includes a plurality of such processes and reference to “the dielectric material” includes reference to one or more dielectric materials and equivalents thereof known to those skilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and “includes” when used in this specification and in the following claims are intended to specify the presence of stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, acts, or groups. 

1. A method of cleaning a dielectric window comprising: flowing a halogen-containing precursor into a substrate processing region while forming a first local plasma in the substrate processing region having a first local plasma power to form excited halogen-containing species, wherein a copper residue on interior surfaces of the dielectric window is transformed into a copper halogen layer on the dielectric window; flowing an inert gas into the substrate processing region while forming a second local plasma in the substrate processing region having a second local plasma power, wherein the copper halogen layer is desorbed as desorbed species from the dielectric window and wherein the second local plasma occurs after the first local plasma.
 2. The method of claim 1 wherein the desorbed species of the copper halogen layer are exhausted from the substrate processing region during or after the second local plasma.
 3. The method of claim 1 wherein the halogen-containing precursor comprises chlorine.
 4. The method of claim 1 wherein the halogen-containing precursor comprises at least one of bromine or iodine.
 5. The method of claim 1 wherein the inert gas comprises helium.
 6. The method of claim 1 wherein the substrate processing region consists essentially of one or more of hydrogen, halogens, inert elements and desorbed species during the second local plasma.
 7. The method of claim 1 wherein the substrate processing region consists essentially of inert gases and desorbed species during the second local plasma.
 8. The method of claim 1 wherein the first local plasma and the second local plasma are each attained using inductively-coupled power.
 9. The method of claim 1 wherein the first local plasma power is between about 50 watts and about 2500 watts.
 10. The method of claim 1 wherein the second local plasma power is between about 100 watts and about 5000 watts.
 11. The method of claim 1 wherein the substrate processing region is devoid of halogens during the second local plasma aside from the desorbed species.
 12. The method of claim 1 wherein a pressure within the substrate processing region is between about 0.5 mTorr and about 500 mTorr during the first local plasma.
 13. The method of claim 1 wherein a pressure within the substrate processing region is between about 0.5 mTorr and about 500 mTorr during the second local plasma.
 14. A method of cleaning a dielectric window comprising: flowing a halogen-free precursor into a substrate processing region while forming a subtractive etch local plasma in the substrate processing region having a subtractive etch local plasma power to form excited halogen-free species, wherein the subtractive etch local plasma etches copper from a substrate and leaves a copper residue on the interior surfaces of the dielectric window; removing the substrate from the substrate processing region; flowing a halogen-containing precursor into the substrate processing region while forming a halogen local plasma in the substrate processing region having a halogen local plasma power to form excited halogen-containing species, wherein the halogen local plasma transforms a copper residue on interior surfaces of the dielectric window into a copper halogen layer; and flowing an inert gas into the substrate processing region while forming an inert gas local plasma in the substrate processing region having an inert gas local plasma power, wherein the copper halogen layer is desorbed as desorbed species from the dielectric window and wherein the inert gas local plasma occurs after the halogen local plasma.
 15. The method of claim 14 wherein the substrate processing region is devoid of halogens during the subtractive etch local plasma. 